A New Approach to Falls
Step-speed enhancement can improve balance in the elderly
October 16, 2013
Age-related changes such as a reduction in visual acuity, reduction in reflexive movements, postural changes, arthritis, and loss of muscle mass can increase risk of falls in the elderly. There is a strong relationship with loss of muscle mass and strength, and age-related muscle loss is defined as sarcopenia.
Muscle loss is mostly seen in inactive individuals; it is also apparent to those who are physically active throughout their lives. Many factors contribute to muscle loss in addition to inactivity -- reduction in hormonal levels, reduction in synthesis of proteins, and loss of motor units. Exercise and strength training has been proven to reduce the rate of muscle mass loss.
Inactivity exacerbates motor units loss, especially fast-twitch motor units. A motor unit consists of the motor neuron and the muscle fiber it enervates. The nervous system dictates the speed of the motor unit recruitment, and recruitment is determined by the amount of force the muscles are required to produce in order of size, starting with the smaller motor unit with the fewest fibers to the larger motor unit with the most muscle fibers.
Slow- and Fast-twitch Muscles
Motor units are referred to as slow-twitch oxidative, fast-twitch oxidative and fast-twitch glycolytic. When a motor unit fires, all the muscle cells in that particular motor unit contract with 100% intensity; the muscle cells either contract 100% or not at all.
When differentiating between slow- and fast-twitch motor units, the fast-twitch motor units control more muscle cells, and these cells are larger and can produce more force.
Motor neurons will die with age, resulting in de-enervation, which causes the muscle fiber to atrophy and die. In time this can lead into reduction of muscle mass. Slow-twitch motor units have slower firing rates, are slower to contract, and are smaller in fiber number. With the increase of fast-twitch neuron death, slow-twitch muscle compensates, resulting in remodeling.
A remodeled slow-twitch will result in less-controlled, less-precise movement with less force production.1 As one ages, the numbers of spinal cord motor neuron and functioning motor units decline.
Step speed and initial recovery compensatory step shows to be a significant factor in withstanding the challenge of perturbation.2 Using a safety harness, a computer-controlled treadmill can be used to target performance of compensatory response. The risk of falling after the laboratory-induced trip response was reduced by 83%.
Wu, Ji, Jin and Pai found that increase in initial forward velocity and greater forward shift of the center of mass requires following with an increase in minimal step length needed for balance recovery.
Balance, strength and gait training are just a few strategies used to improve posture reaction to avoid perturbation. Research presented by Chung and Pai of the University of Illinois Chicago exposed individuals to unstable conditions on a controlled, moveable platform to mimic a "slippery floor." In the study, eight participants trained on the movable platform a total of 37 times. The platform was set up so that it would release unannounced 24 of those times. This release causes a frontward or backward slip.
The researchers found that none of the trained participants fell on the slippery floor, and seven of the eight never lost balance. This study demonstrated neuro-adaptation to a fall prevention strategy, thus the ability to quickly learn to maintain balance and avoid a slip-related fall. Induced stepping has been coupled with increased skill retention.
DePasquale developed the RIPPS (repeated incremental predictable perturbation in standing) Method, a first attempt, single-failure protocol to quantify forward and backward stepping limits. RIPPS is both reactive and anticipating perturbation using a spring scale test.
Step Speed Enhancement
The introduction of "Step Speed Enhancement" is a concept developed by this author in which focus is drawn to motor unit recruitment, strength training, improving step speed reaction and maximal step length to allow optimal ability to effectively respond and react to perturbation. Initiating a learning process by acquired reflexive training by repetition and to induce speed of movement without thought can be applied to summons ability to withstand perturbation and reduce risk of falls.
The Step Speed Enhancement Protocol includes four maneuvers:
1. Color Target Step Maneuver
Items needed: Stopwatch, gait belt, colored circle targets, and 9 index cards. A floor pad is used with different colored spots approximately 9 inches in diameter. These target spots are approximately 10 inches from each other, and 10 inches from the foot placement starting point. From left to right the colored targets are red, green, purple, and blue; the yellow targets are just posterior to both feet.
Directions: The subject stands on the designated starting position on the pad. Nine index cards have various directions to move either the left or right foot to the designated colored target spot as quickly as possible, and return to the starting position. For instance, the caller reads the card and directs the subject "Left foot Blue." The subject steps on the target and returns. The next card reads "Right foot Red," and the subject steps onto the red-colored target and returns. Upon calling directions from the index cards, a timer is initiated. When the caller calls all nine directional cards, the timer is stopped. The caller shuffles the index cards and another series is randomly performed.
Purpose: Timed speed stepping reacting to unplanned patterned directions by means of verbal instructions and random colored targets in various planes of movement. Speed of movement is measured by stopwatch, and progress is monitored. Progress is measured by speed and step target (increase challenge by step crossing past midline and retro stepping as an instruction on an index card). Gait belt is used for safety.
2. Timed Maximal Step Maneuver
Items needed: Stopwatch, 12-foot 2x2 board with 1-inch hole increments, colored pegs.
Directions: The 12 ft 2x2 board is placed on a level surface. The subject stands perpendicular to and in the middle of the 2x2 board. The subject is asked to stand at a comfortable position at the middle of the 2x2 board. Red pegs are placed perpendicular to each foot as markers to identify the starting point. The subject is asked to step out as far as possible, in this case lateral stepping (abduction), and a green peg is used to mark foot placement to identify the subject's maximum lateral stepping. The subject is instructed to return to starting position. The subject is then instructed to do the same maneuver to the other side, and maximal step is again marked with another green peg and instructed to return to the starting position. The subject is then instructed from the starting position (red pegs) to step laterally to the maximum step target (green peg) as quickly as possible, alternating from one side to other, facilitating weight shift and offloading. A timer is started once the subject begins. A series is considered after the maneuver is performed to the left and then the right. The timer stops after completing 4 series. A "target peg" is used as a yellow peg to mark the maximum target. This author uses one-third of the total height of the subject -- for instance, if the subject is 6 feet tall, the "target peg" is measured and placed 24 inches from each foot's starting point. This will be considered a maximal target goal. The same maneuver can be applied upon frontal plane stepping.
Purpose: This maneuver measures maximum step length and step speed using pegs as visual markers to target and also record progress. The board having holes increments of 1 inch can easily measure step placement. The concept of facilitating faster step speed over the greatest stepping distance can allow for improved chance in reducing falls due to perturbation.
3. Induced Reflexive Step Manuever
Items needed: Wide belt such as weightlifting belt, Theraband™, a quick-release clamp/hook.
Directions: A wide belt or, in this setting, a weight lifter belt (to allow greater surface contact on the subject and improve comfort) is applied to the subject. The belt has an "O" ring or band attached. One end of a blue theraband is attached to a hand rail, and the other end has a spring-shut clamp. The subject faces the hand rail three feet away with both feet together. The 1-foot blue theraband is stretched over three feet and the clamp is attached to the "O" ring on the belt. The subject is pulled via theraband, promoting a perturbation under supervision. The generated pull will only be enough to facilitate a reflexive step to react toward the direction of pull. Variation in theraband color, tension and distance of stretch will determine force. Theraband offers a band-to-weight conversion chart. This is only a first-step non-anticipated reaction maneuver. This maneuver can be applied to all planes in standing positions. Progress can be measured by subject's initial step reactions with greater pull force.
Purpose: Under controlled and supervised conditions, the subject's balance is challenged by a forced pull, allowing a reflexive step response toward the direction of pull. The concept is that the subject is being "trained" to step react to various controlled and measured forces of directional pull.
4. Multi-dimensional Strengthening Maneuver
Items needed: Weightlifter belt, or wide gait belt, and Theraband.
Directions: Apply the belt around the subject's waist. Attach one end of a 1-foot piece of theraband to the lateral aspect of the belt and the other end to a stable base such as parallel bars or handrail. Have the subject side step away from parallel bars, stretching the theraband at approximately twice its length. Have the subject hold position, then instruct the subject to step forward and back, alternating steps; this is in conjunction with the lateral pull of the theraband. The subject is then asked to side step left to right and cross over midline left to right. The theraband is removed, then applied posteriorly to the belt, and subject is again instructed to pull away. The subject again is instructed to lateral side step, forward and back, stepping and crossing over left to right; this time the force pull is posterior. The theraband is attached to the belt anteriorly, laterally and posteriorly to create a multi-dimensional exercise. Different color/tension therabands can be used to vary force pull.
Purpose: A closed chain variable forced pull exercise to strengthen, challenge balance and improve postural awareness to and maximize ability to react positively to multidimensional postural challenges.
In case studies, the Step Speed Enhancement Protocol showed an overall increase in step speed and step length with participating subjects. One can conclude that with improved ability to step faster over a greater distance, patients can reduce the chance of perturbation.
The step speed enhancement protocol is a method of balance, coordination and strengthening exercises that offers a visual measurable goal using inexpensive equipment. Further studies are indicated for long term effectiveness and contribution to fall prevention.
1. Bhatt, T., Pai, Y.-C. (2009). Generalization of gait adaptation for fall prevention: From moveable platform to slippery floor. Journal of Neurophysiology.
2. DePasquale, L, Toscano, L. The Spring Scale Test (SST): A Valid and Reliable Tool for Explaining Fall History. The Journal of Geriatric Physical Therapy, 2009, 32(4), 159-167.
3. Sarcopenia: The Mystery of Muscle Loss Chantal Vella, M.S. and Len Kravitz, Ph.D.
Acknowledgement: Dr. Amy Sun , Dr Andrew Mantelman.
Tom Dicarlo is director of rehab and master clinician with Aegis Therapy at St. Matthews Center for Health, Park Ridge IL, and a member of The Illinois Falls Coalition.